Charge forming device



July 14, 1936.

F. E. AsELTlNE CHARGE FORIING DEVICE Filed Aug. .9, 1929 2 sheets-sheet 1 Jrea seliz'ne July 14 1936- F. E. AsELTlNE I 2,047,899

CHARGE FORMING DEVICE Filed Aug. 9, 1929 2 Sheets-Sheet 2 E im 3mm fred selfz'rze Patented July 14, l936` PATENT OFFICE cnAnGE FoaMlNG DEVICE Fred E. Aseltine, Dayton, Ohio, assigner, by mesne assignments, to General Motors Corporation, Detroit.. Mich., a corporation of Dela- Ware i Application August'9, 1929, Serial No. 384,726

33 Claims.

This invention relates to charge forming devices for internal combustion engines and more particularly to devices of this character which comprisev a plurality of primary carburetors, which deliver ,a primary mixture of fuel and air to a plurality of secondary mixing chambers located adjacent the engine intake ports and in which the primary mixture is mixed with additional air under certain operating conditions.

A device of this character is described in the co-pending application of Fred E. Aseltine, Wilford H. Teeter, and Carl H. Kindl, Serial No. 288,683, filed June 27, l1928.

It is the principal object of the present invention to provide improved means for enriching the mixture during the acceleration period. Withv this object in view, the invention consists primarily in the provision of means to supply additional fuel to the primary mixture passages, which convey primary mixture from the primary carburetors to the secondary mixing chambers, and simultaneously to the secondary air passage, which supplies additional air to -the said secondary mixing chambers to be mixed with thev pri- 'mary mixture, as above set forth.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of. the embodiment of the present invention is clearly shown.

In the drawings: Fig. 1 is a vertical, longitudinal section through a charge forming device constructed in accordance with. the present invention and the intake port with which it is associated.

Figs. 2 and 3 are fragmentary, detail sections on the lines 2 2, 3 3 of Fig. 1.

Fig. 4 is an elevation of a carburetor unit in manifold lll, having three outlet branches, thev middle branch l2 being shown herein.. Each of these branches communicates with one of theintake ports I4v of a multicylinder engine. The outlet branches are each provided with an attaching ange I6 for securing the manifold to the engine block in the usual manner, and a ange I8 to which the carburetor unit issecured.

The carburetor unit comprises a main housing 20, having an attaching flange 22, adapted to be secured to the ange I8 by screws 24. An air inlet coupling 28 is secured in position to register with an opening in the upper wall of the housing 20, in any suitable Way and may be connected 5 with an air cleanerrif desired. A casting 30, in which the passages supplying fuel to the nozzles are formed, is secured by screws to the lower wall of housing 20, and a sheet metal fuel bowl 32 is held tight against an annular shoulder 34 on the 10 housing by any suitable means. Fuel is conducted from a main source of supply to the fue! bowl through a conduit (not shown) and the iiow of fuel to the bowl is controlled by a iioat 36, operating in the usual manner to maintain a sub- 15 stantially constant level of fuel therein. l.

Fuel flows from the bowl 32 to a plurality of primary fuel nozzles 38, one of which is located in each of the primary mixing chambers 40, the construction ofwhich is briefly described hereinafter. The fuel conduit between the fuel bowl and the nozzles comprises the vertical fuel passage 42 communicating at its upper end with the horizontal fuel canal 44, which connects with each of the nozzles 38 through an orifice 46. Fuel 25 is admitted from thefuel bowl to the passage 42 at all engine speeds, through a fixed metering orifice 48 and at high speeds additional fuel is admitted through an orifice 50 controlled by a valve-52, operated in the manner set forth in the 30 above mentioned application. 'Ihis operating means forms no part of the present invention and need not be described further herein.

Fuel is lifted from the fuel bowl through the l above described fuel passages and nozzles 38 to 35 the primary mixing chambers by the suction therein. Opening movements of the throttle cause a reduction in mixing chamber suction which might permit the fuel column to drop sufflciently to cause a temporary fuel starving of the engine unless means are provided to prevent this action. For this purpose a check valve 54 is provided in an enlarged chamber 56 at the junction Yof the channels 42 and-44, and on reduction of mixing chamber suction, seats on the bottom of the chamber, preventing downward flow of fuel.

Each primary fuel nozzle is provided with a main fuel outlet 58 in the top of the nozzle and a secondary' fuel outletcomprising two orifices 60 and B2 in the vertical wall of the nozzle near 50 the bottom of the mixing chamber. At relatively high speeds, the mixing chamber suction is sulcient to lift fuel from the main outlet as well as from orifices 60 and 62. At idling, or low speed( operation under load, however, thesuctionds enough to lift fuel only to some point between the top of the nozzle and the orifices 68 and 62, fuel flowing from these orices by thev bers from the remainder of the mixture passages' to reduce the velocity of flow past the fuel nozzles -for the purpose fully set forth in the above mentioned copending application.

A single throttle valve 68, which extends across all the primary mixture passages, controls the ow therethrough and is provided with grooves 18, which register with said mixture passages. This throttle is operated in a manner hereinafter more fully described. l The middle primary mixture passage communicates with a tube 12 fixed in the manifold branch |2.l This tube constitutes one of the primary mixture conduits above referred to and conveys the primary mixture to the secondary mixing chamber located in the middle branch of the manifold.

Nearly all of the air entering the carburetor flows through the inlet coupling 28 and is controlled lby the main air valve 14, normally held against a. seat 16 by a spring 18, received between ythe valve and a flange 88, projecting from a sleeve 82,- slidably mounted on a stationary guide sleeve 84, xed in the housing 28, and serving also as a guide for the stem 86 to which the air valve is secured. When it is desired to choke the carburetor to facilitate starting of the engine, the ange 88 is adapted to be, lifted by means not shown herein, but fully described in the above application, until the upper end of the sleeve 82 engages the air valve to hold it closed. Suicient air to carry the starting fuel from the nozzles to the intake ports is admitted through an elongated slot 81, formed in a plate 88, secured to the housing 28, as shownA in Fig. 1.

The valve 14 admits air to the air chamber 98, from winch air flows to the, primary passage through an orifice 92 in the bottomof the air chamber and to the secondary mixing chambers Y through a passage 94, which connects with the inlet of the manifold I8.` The-flow of air through this passage is controlled by a manually oper-.- able throttle 96, secured to a shaft 98, rotatably mounted inthe main housing and by a suction operated valve |88, secured to a shaft |82, also rotatably mounted in the main housing.

` While the means for operating the primary and secondary throttle valves is nopart of the present invention, rsuch Fig. 5 and is briefly described hereinafter for the purpose of enabling a more ready understanding of the operation of the device in general. An operatlng arin |8| is secured to a spindle |83 projecting from one end of the primary throttle 61 outside the main housing 28, said operating arm being provided with an orifice in the*` free end in which some suitable form 'of operating connection may be attached. 'Ihis operating arm is connectedby a suitable lostfnotion connection to an arm |85 secured by asplit clamp or any other suitable means to one end of the shaft98,

mechanism is shown inA outside. the main housing. An operating link |81', forming part of the lost motion connection is pivotally connected to the operating arm |8|, while a pin |89 projects from the arm |85 through a slot in said link. A regulating screw ||3 is threaded in lugs I5 projecting from the operating link and may length of the slot the upper end of said screw forming the lower end of the slot. A tension spring ||1 is connected at one end to the upper end. of the link and at the other end to the pin |89, said spring tending to hold the pin against the upper end of the slot With both throttles closed the parts are in the position shown in Fig. 5 with the pin |89 in engagement with the screw ||3. As the arm |8| is rotated in a counter clockwise direction to` open the primary throttle be adjusted to regulate thel valve, the link moves downwardly until the upl dependent movement of the primary throttle,

' but said screw is generally so adjusted that the primary throttle may move without accompanying movement of the air throttle until the engine speed corresponds to a vehicular speed of approximately 28 to 25 miles per hour on a level.

On opening of one or both of the throttle valves, the suction in the air chamber 98 is increased and the valve 14 is opened to admit additional air and increase the quantity of mixture supplied to the engine.' The opening of this valve is retarded to prevent uttering of the valve and to restrict the admission of air so as to enrich the mixture to some extent whenever the throttles are opened. For this purpose a dashpot is provided comprising a cylinder 4|84 which receives fuel vfrom the reservoir 32, and a piston |86, secured to the lower end of the valve stem 86 by any suitable means. A check valve is provided inthe bottom of the dash pot cylinder, as shown in the above application, to admit fuel thereto on closing movements of vthe valve and `to prevent escape of fuel therefrom as the valve is opened. The specific construction of this dashpot is not material so far as this invention is concerned, and may be any conventional" form of liquid dashpot which will properly retard the opening of the air valve.

'As hereinbefore stated, the valve |88 is opened by engine suction when the air throttle 96 is opened. In earlier devices of this type such as that disclosed in the Vabove mentioned copending application, a dashpot has been provided for the purpose of retarding the opening of the valve |88 whenever the air throttle 96 is opened. The y'purpose of this dashpot and its construction are fully disclosed in the application referred to, but its function is briefly set forth here in order to facilitate a clearer understanding of the present invention. If the valve |88 were allowed to open freely, the air admitted'through the passage 94 would reach the secondary mixing chambers before the increased quantity of primary mixture resulting from the opening of the throttle and the mixture formed in the secondary mixing chambers would, therefore, be too lean to properondary mixing chambers is substantially that voperate as a fuel fuel' delivery tube required for the increased supply of primary mixture to reach said mixing chambers.

'I'he use of the dashpot has not been altogether satisfactory for the reason that the retarding 'effect is not always just that desired, and it has been found that unless the dashpot is constructed within very narrow limits of accuracy diiiculties arise. In other words the dashpot is too sensitive and production somewhat dicult for this reason. In a device constructed in accordance with the present invention, however, it has been found that the dashpot can be less accurately made without disturbing the functioning ofthe carburetor and the problems of manufacturing correspondingly simplified.

These results are accomplished by the provision of, a pump operated on opening movements of the throttle and so constructed that it supplies fuel not only to the primary mixture passages as in the earlier application referred to, but also to the secondary air passage 94 during theacceleration period. To this end the dashpot cylinder 04which operates as a retarding means for the main air valve, is also constructed to pump and for this purpose a |08 is connected near the bottom of the cylinder |04, as shown in Fig. 1, and is connected at its upper end in a block 0,

'secured to the lower side of the main housing within the fuel bowl and above the level of fuel therein. The tube |08 communicates at its outlet erd with a channel 2 extending transversely ofthe block ||0 and communicates directly with three vertical passages ||4, each of which communicates with the vertical passage H6, formed in the bottom wall of the main housing, as indicated in Fig. 3. The passages lI6 communicate with the primary mixture passages and supply fuel directly thereto on operation of the pump in the manner fully described in the above mentioned copending application. A fuel passage ||8, shown in dotted lines in Fig. 1, connects with the passage ||2 and also connects with a vertical passage |20, bored in the block ||0 and communicating with a similar passage |22 bored in the wall of the main housing and extending upwardly to the secondary air passage with which it connects to deliver fuel thereto, as shown in Fig. 1. Two air passages |24 are provided which admit air to the fuel passage ||2 to form an emulsion of fuel and air therein and to reduce the suction communicated to the passage |26 from the primary mixture passages sufficiently to prevent fuel being drawn upwardly from the cylinder |04 to the passage |26 by the engine suction in a manner fully described in the earlier application. It will be noted that the passage |20 is provided with' a` restriction at |26 to limit the supply of. fuel forced by the pump to the air passage 94. This restriction may be of whatever size is Vdesired to give the most satisfactory results.

It will be clear that on operation of the above described, pump, fuel is simultaneously injected into the primary mixture passages and the secondary air passage, the fuel delivery passages being of the desired size to Supply the desired quantity of additional fuel at the points referred to. By injecting fuel into the air supplied to the secondary mixing chambers through the passage 94, the retardation of the opening of valve |00 need not be so accurately timed as in the earlier device, and since the air passing through the passage 94 is impregnated with fuel by the action per position by a spring reaching the secondary mixing chambers before the increased quantity of primary mixture is not so marked as in said earlier device.

In the form of the invention disclosed in Fig. 4, the pump is operated by the primary throttle vinstead of the air valve. To this end an operating arm |30 is secured by a screw |32 to one end of tne primary throttleand at its other end is pivotally connected to a piston rod |34 which operates the pump piston. The lower end of the rod projects into a tube |36 slidably mounted on the pump piston and provided with a closed lower end. A flange |38 is formed at the bottom of this tube and is slidable in a small cylinder |40 in the pump piston |42 and closed by a screw cap |44 as shown in Fig. 4. A spring |46 is received within the cylinder |40 and normally holds the tube in the position shown in the drawings with the flange |38 in engagement with the top of piston |42. The piston |42 is slidable in the cylinder |48 and is normally held in itslpder between the piston and the bottom of said cylinder. The piston rod is not connected to the tube .36, but merely engages the closed bottom end of said tube to move the bottom downwardly on downward movement of the rod.

An orifice |52 in the cylinder wall connects with a fuel delivery passage |54 leading to a channel |56 identical with the channel |26 and formed in a block |58 identical with the block 24.

A check talve |60 is received in a valve cage |62 mounted in an enlargement |64 in the fuel delivery passage and prevents return of the column of fuel from the deliveryrpassage to the pump cylinder when the pump is not operating.

The operation of this pump should be obvious on inspection of the drawings. The arm |30 lrocks downwardly on any opening movement of the throttle, depressing rod |34 and moving the tube |36 downwardly. This compresses the spring |46 and puts the air in cylinder |40 under pressure, which is effective to move the pump pis-v ton downwardly as soon as the resistance of spring |50 is overcome whichwill be almost immediately after the downward movement of the piston rod begins. The mechanism disclosed thus forms a slightly yielding connection between the throttle and the pump piston by means of which jar on the parts during operation is avoided. Downward movement of the piston |52 forces fuel through the delivery passage |54 and the passages in the block |58 to the primary mixing chambers and the secondary air passage in the manner set forth in describing the form shown in Fig. 1.

The construction of fuel delivery passages from the channel |56 to the fuel outlets is just the same as in the device disclosed in Fig. 1 and the remainderof the carburetor, other than the specific pump shown in Fig. 4 is also identical with that disclosed in Fig. 1. lTherefore the specific description of such structures need not be repeated.

The secondary mixing chambers are identical and each comprises a Venturi tube |42 positioned adjacent the outlet end of the primary mixture conduit. Each venturi is provided with an exsembled. The Venturi tubes serve to accelerate the flow through the primary mixture conduits in the manner fully disclosed in .the earllerapplication.

. ,1. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air-passage supplying vadditional air,- a throttle, and a pump operated on opening movements of the throttle to positively inject fuel into the mixture passage and the secondary air passage. 2. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additional air to the mixture passage at a point relatively remote from the fuel supply, a throttle, and a' pump operated by the throttle to positively inject fuel into the: secondary air passage and the mixture passage. l

` 3. A charge forming device for internal combustion engines comprising. a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additional air,.a throttle, a manually operable valve in said secondary air passage,4 and means operative on opening movements of the throttle to supply fuel 'tosaid secondary air passage posterior to said valve.

4. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additionalair, a throttle, a valve in secondary air passage operable concurrently with thel throttle and means operative on opening movements of the throttle to supply fuel to said secondaryA air passage posterior to said valve.

5. A charge forming device for internal` combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additional air, a throttle, an air valve in said secondary air passage, means for opening said valve after the throttle has made a predetermined opening movement, and means operable on all opening movements of the throttle to supply fuel to said secondary air passage anterior to said valvel whereby any fuel supplied to the secondary air passage before the opening of said air valve will l accumulate in said passage until the' valve is opened.

6. A charge forming device for internal combustion engines comprising a mixture passage,

means for supplying fuel and air thereto, a secondary air passage supplying additional air, a

throttle, suction and manually operated valves inthe secondarypair passage L,and means oper- 'ated on opening movementsof the throttle for supplying fuel to the secondary air passage at apoint between the two valves.

'1. A charge forming device for internal com-- bustion engines comprising a mixture passage,

means for supplying fuel and air thereto, a secondary air passage supplying additional air, a throttle, avalve in the secondary air passage adapted'to be opened as the throttle is opened on opening movements of to said secondary air and means operated the throttle tolsupply fuel passage posteriorto said valve and to said mixture passage anterior to the throttle.

8. A charge 'forming device forzinternal com- .to, a secondary mixing chamber into which tle for regulating the fiow -said valve.

bustion engines comprising a mixturepassag'e, means for supplying fuel and air thereto, a sec-v ondary. air passage supplying additional air, a throttle, a valve in the secondary air passage adaptedto be opened as the ythrottle is opened and a pump operated by the throttle for injecting fuel into the secondary air passage posterior to said valve and into the mixture passage anterior to the throttle.

9. A charge formingdevice for internal combustion vengines comprising a primary mixture passage, means for supplying fuel -and air thereto, a secondary mixing chamber into which the primary mixture passage is adapted to deliver a primary mixture of fuel and air, a primary throttle for regulating the flow through the primary mixture passage, a secondary air passage for supplying air to the secondary mixing chamber, and means operative on opening movements of the primary throttle to supply additional fuel to the primary mixture passage and to supply fuel to the secondary air passage.

10. A charge forming device for internal combustion engines comprising a, primary mixture passage, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture passage is adapted to deliver a primary mixture of fuel and air, a primary throttle for regulating the flow through the pril a secondary airv passage secondary mixing chammary mixture passage, for supplying air to the ber, and a pump operated on opening movements of the primary throttle to inject fuel into the secondary air passage and primary mixture passage.

11. A charge -forming device for internal combustion engines comprising a primary mixture passage, means for supplying fuel and air thereair passage and primary mixturepassage.

12. A charge forming device for internal combustion engines comprising a primary mixture passage, means for supplying fuel andair theee primary mixture passage is adapted to deliver a primary mixture of fuel and air, a primary throtthrough the primary mixture passage, a secondary air passage for supf plying air to the secondary mixing chamber, a

` pump for supplying fuel to the secondary air pas- Amixture passage and means,

sage and primary connecting the pump to the primary throttle' for operation therewith.

' 13. A charge forming device for 'internal com bustion engines comprising a primary mixture passage, means for supplying fuel and air thereto, asec'ondary mixing chamber into which the primary mixture passage is adapted to deliver a primary mixture of fuel and air, a primary throttle for regulating the flow through the' primary mixture passage, a secondary air passagefor supplying air to the secondary mixing chamber,. a

-valve in said secondary air passage adapted "to be opened as the throttle is opened and means operated as the throttle is opened for supplying fuel to said secondary air passagel'po'sterior to 14. A charge forming device for internal combustion engines comprising a primarylmixtureis passage, means for supplying fuel and air thereto, a' secondary mixing chamber into which the primary mixture passage is adapted to deliver av ary mixing chambers, a plurality of primary mixturel passages adapted to deliver a mixture of fuel and air thereto, means for supplying fuel and air to said primary mixture passages, a primary throttle regulating the flow through said mixture passages, a secondary air passage -for supplying air to all of said secondary mixing chambers, and means operated as the primary throttle is opened for supplying fuel to the secondary air passage. y

16. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary mixture passages adapted to deliver a. mixture of fuel and air thereto, means for supplying fuel and air to said primary mixture passages, a primary throttle regulating the. flow through said mixture passages, a secondary air passage for supplying airto all of said secondary mixing chambers, and means operated as the primary throttle is opened for supplying fuel to the secondary air passage and to all the primary mixture passages.

17..'A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary mixture passages adapted to deliver a mixture of fuel and air thereto, means for supplying fuel and air to said primary mixture passages, a primary throttle regulating the flow through said mixture passages, a secondary air passage for supplying air to all of said .secondary mixing chambers, a valve in the secondary air passage adapted to be opened as the primary throttle is opened and means operated by said throttle during its opening movements for supplying fuel to said secondary air passage posterior to said valve and to said mixture passages anterior to the throttle.

18. A charge forming device forinternal combustion engines comprising a'mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additional airfa throttle, a pump operated on opening movements of the throttle to inject fuel into the mixture passage and secondary air passage, a fuel delivery passage leading from the pump to said mixture passage and secondary air passage, and means to admit air to said fuel delivery passage.

19. A charge forming device for internal combustion. engines comprising a plurality of primary mixture passages adapted to deliver a primary mixture of fuel and air to a pluralityof secondary mixing chambers, va secondary air passage for supplying air to said secondary mixing chambers. a fuel pump operative on opening movements of the throttle and having a fuel delivery passage lleading to all of said primary mixture passages and the secondary air passage, and means for admitting air to said fuel delivery passage.

20. A charge forming device for internal combustion engines comprising a mixture passage,

means for supplying fuel and air thereto, a secondary air pamage supplying additional air, a

throttle, a valve in said secondary air passage,

' means connecting the valve with said throttle for operation thereby, and a pump also operated by the throttle for supplying fuel to both the primary mixture passage and secondary air passage during the acceleration period.

21. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying additional air, a throttle, a valve in said secondary air passage, means connecting the valve with said throttle for operation thereby, said means being so constructed that the valve is not opened until after a predetermined opening movement of the throttle,

`and a pump operated by the throttle for supplying fuel to both the primary mixture passage and secondary air passage during the acceleration period.

22. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a secondary air passage supplying'additional air, a throttle, a valve in said secondary air passage,

means connecting the valve with said throttle for operation thereby, said means being so constructed that the valve is not opened until after a predetermined opening movement of the throttle, and a pump operated by the throttle for supplying fuel to both the primary mixture passage and secondary air passage during the entire opening movement of the throttle.

23. A charge forming device for internal combustion enginesv comprising a mixture passage,

means for supplying fuel and air thereto.' a secondary air passage having a valve therein for supplying additional air, a throttle, a main air valve for controlling the admission of air to both the mixture passage and secondary air passage, and means operated by the main air valve for supplying fuel to the mixture passage and secondary air passage during the acceleration period.

24. A charge forming device for hinternal combustion engines comprising a mixture passage, means for supplying fuel and air thereto. a secondary air passage having a valve therein for supplying additional air, a throttle, a main air valve for controlling the admission of air to both the mixture passage and secondary air pas- Sage, and a fuel pump operated by the main air valve for injecting fuel into the mixture passage and the secondary air passage on opening movements of the throttle.,

25. A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a throttle controlling the ow of fuel mixture, a secondary air passage, a valve in said secondary air passage adapted to be opened after a predetermined opening movement of the throttle,

' a main air valve controlling the admission of rlocated adjacent the engine intake ports, and

relatively remote from the fuel inlet, into which the primary mixture passage delivers a primary mixture of fuel and air, a primarythrottle for controlling the primary mixture passage, a secondary air passage for supplying air to the secondary mixing chamber, and a pump operated by the primary throttle for injecting fuel into the mixture passage and secondary air passage on opening movements of said throttle.

28. A charge forming device for internal combustion engines comprising a primary mixture passage, air and fuel inlets for supplying fuel4 fand air thereto, a secondary mixing chamber located adjacent the engine intake ports, and

relatively remote from the fuel inlet, into 'which the Vprimary mixture passage delivers a primary mixture of fuel and air, a primary throttle for controlling the primary mixture passage, a secondary air passage for supplying air to the secondary mixing chamber, a main air valve controlling admission of air to the mixture passageV and secondary air passage, and means operated by said air valve for supplying fuel to the mixture passage and secondary air .passage as the throttle is opened.

29. -A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers located adjacent the engine intake ports, a plurality of primary mixture passages adapted to deliver a primary mixture of air and fuel thereto, fuel and air inlets therefor relatively remote from the secondary mixing chambers, a secondary air passage for supplying additional air to all the secondary mix- 'ing chambers, va primary throttle for regulating the flow of primary fuel mixture, an air valve controlling the admission of air to the secondary air passage and primary mixture passages, and means operated by the air valve for supplying fuel to said air and mixture passages as the throttle isA opened.

30. A charge forming device for internal combustion ,engines comprising a main housing having a mixture passage and secondary air passage formed therein, fuel and air inlets for Supplying fuel and air to said mixture passage, a throttle regulating the now of fuel mixture through saidk mixture passage, a fuel distributor block having Va plurality of fuel passages formed therein, a

fuel pump having a fuel delivery passage supplying fuel to the passages in said distributor block, and fuel passages formed in the main housing connecting the passages in said distributor block with the mixture passage and secondary air passage. u

31. A charge forming device for internal combustion engines comprising a mai housing having a mixture passage and secondary air passage formed therein, fuel and air inlets for supplying fuel and air tosaid mixture passage, a throttle regulating the flow -of fuel mixture through said mixturepassage, a fuel distributor block havinga plurality of fuel passages formed I a single secondary air passage formed therein,

fuel and-air inlets for supplying fuel and air to said primary mixture passages, a primary throttle regulating the flow of fuel mixture through all of said primary mixture passages, a fuel distributor block having a plurality of fuel passages formed therein, a fuel pump having a. fuel delivery passage supplying fuel to the passages in said distributor block, and fuel passages formed in the main housing connecting all of the primary mixture passages and the secondary airv passage with the fuel passages in said distributor block.

33. In a carburetor, a secondary mixing chamber, a primary mixture passage adapted to deliver a primary mixture of fuel and air to .said secondary mixing chamber, a primary throttle valve in said mixture passage for controlling the flow ofv mixture therethrough, a fuel reservoir, an acceleration device-comprising a fuel chamber having a restricted connection to the fuel reservoir, an actuating member movable in consonance with throttle position, a fuel-displacing member in said chamber slidably related to the actuating member, resilient means transmitting the force of the actuating member to the fueldisplacing member, and means for delivering fuel from saidacceleration device both to the primary mixture passage and the secondary mixing chamber. 

